Spectrally and Temporally Engineered Processing using PhotoElectroChemistry (STEP-PEC)

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

Abstract: Non-Technical: Semiconductor devices are ubiquitous. They represent a multi-trillion dollar industry. Ordinary objects such as electrical outlets, thermostats, and blood pressure/heart rate monitors, are being embedded with increasingly complex control electronics, sensors, and network connectivity to enable greater functionality, value, and service. Although foundry services exist for large volume manufacturing of microelectronics for ?smart? objects, there are no cheap (<$100/run) rapid turnaround (<1hr) options for garage inventors to prototype new ideas. The biggest hurdles are that conventional microfabrication requires a cleanroom and expensive (>$1M) equipment. This NSF project seeks to democratize semiconductor manufacturing by investigating a new fabrication paradigm in which pulses of light of specific colors catalyze electrochemical reactions that dope, etch, and metallize designated circuit patterns onto a semiconductor wafer with high resolution. The project offers rich opportunities for high school and community college teachers to participate in research and develop teaching modules for hands-on labs through Research Experiences for Teachers projects. Research and teaching will be integrated through the PI?s ?Principles of Experimental Research? course. Graduate and undergraduate students will be trained in semiconductor micro- and nano-fabrication, photonics, optical system design, fluid mechanics, and bio-sensors through the proposed research activities. Recruitment, retention, and participation of students from underrepresented groups will be addressed through Research Experiences for Undergraduates internships and engineering summer camps for 9th-12th grade girls. Results from both research and teaching will be widely disseminated in journals and conferences to enhance the current understanding of photoelectrochemical processing and of engineering education/outreach methodologies. Technical: Photochemical etching uses light to generate minority carriers that catalyze semiconductor wet etching. Recently, the PI?s team implemented photochemical etching using a projector. The local etch rate was controlled using color images drawn in PowerPointTM. Here, the team seeks to drastically improve the etch resolution and anisotropy and expand the method to enable new types of light controlled processes, e.g. patterned doping and metallization, so that new classes of unconventional photonic devices and multifunctional integrated circuits can be fabricated in a single system. In the proposed system, a super-continuum laser, tunable filter, and spatial light modulator will generate high intensity spectrally engineered dynamic image pulses and a synchronized electrical pulse generator will temporally gate the chemical reactions. If successful, this project is potentially transformative because it could create a new semiconductor fabrication paradigm for several reasons. First, multiple processing steps, e.g. doping, etching, and metallization can be performed sequentially in the same system. Second, these processes can be easily aligned to features made through conventional cleanroom processing since the illumination pattern can be adjusted in software. Moreover, this dynamic illumination capability enables new designs to be rapidly prototyped. Next, the processing rate for different bandgap materials can be individually adjusted. Finally, the limitations imposed by conventional planar fabrication technology can be removed and complex 3D devices can be fabricated with precisely controlled dimensions. The overall research goals of this project are to: 1. Understand how spectral and temporal gating affects the resolution, anisotropy, photo-induced selectivity (e.g. light on vs. off), and material selectivity (e.g. GaAs vs. AlGaAs) of the etch; 2. Develop photo-induced electroplating and doping techniques; and 3. Fabricate unconventional devices with complex topography.